Lubricants containing di-phosphorus esters



Patented Apr. 17, 1945 wamoan'rs commune. nr-rnosrnoaUs as'rnns Ernest F. Engelke, Merchantville, N. J., assignor to Cities Service Oil Company, New York, N. Y., a corporation of Pennsylvania 6 No Drawing. Original application March 28,

1942, Serial No. 436,623. Divided and this application December 15, 1942, Serial No. 469,125

9 Claims. (Cl. 252- 53) This invention relates to the manufacture of extreme 'pressure lubricants containing organic dl-phosphorus esters. This application is a division of pending application Serial No. 436,623, filed March 28, 1942.

Many types of extreme pressure agents have been used in lubricating oils and greases andin most cases such agents are relatively unstable and contain constituents which may react with the metal surfaces and induce excessive sludge formation. Reactions of this type materially change the lubricant and gradually deplete its eflective constituents.

The primary object of the present invention is to provide an improved extreme pressure lubricating agent which is relatively stable and which is especially effective in the lubrication of hypoid gears and other mechanisms in which high pressures are involved.

Another object of the invention is to provide improved organic di-phosphorus esters suitable for use as film strength agents. I

In accordance with the features of the present invention the improved di-phosphorus organic esters may be made from the ordinary mono or diorganic phosphites, phosphates or thiophosphates, more particularly the acid halides such as the monochlorides. In general, the improved process includes the steps of reacting the organic phosphorus acid chloride with metallic sodium or its equivalent, at temperatures of from about 150 to about 225 F., the temperature being adapted to effect elimination of the chlorine as sodium chloride and the direct combination of two molecules oi' the acid chloride by a phosphorus-phosphorus linkage.

- The organic phosphorus esters used as starting materials are preferably the monoor dichloride of phosphorus aci Phosphoric acids, and thiophosphoric acids, while the final products may be represented by the general formula:

The compounds, in which the phosphorus is linked to phosphorus with a double linkage, are made from the dichlorides such-for example as (RX) PCl:

pressure lubricants, may be illustrated by reference to the following specific examples in which the quantities of materials are Elven in parts by weight.

Example 1 A tetra-cresyl di-phosphorus ester was prepared from di-paracresyl phosphorus acid monochloride, (CH3.CsH4.0) zPCl, by dissolving approximately 56 parts of the latter in about parts of xylol and heating the resulting solution in a reaction vessel equipped with a reflux condenser. The heating was carried out by the use of an oil bath and the temperature gradually raised to 200 F., at which time five parts of metallic sodium was added to the solution in small portions at a time. The reaction was rather violent and sodium chloride crystals were deposited on the sides and bottom of the reaction vessel. When the reaction was complete, the heating was continued for about one-half hour, and the reaction mass then cooled and filtered to remove the sodium chloride. The filter cake .was washed with hot xylol and added to the nitrat which was washed with water until neutral, and then subjected to distillation for the removal of the xylol. The final stage of the distillation was conducted at a reduced pressure in order. to insure substantially complete removal of the xylol.

The resulting di-phosphorus ester was a straw I,

yellow-colored oily liquid at room temperature. Its effectiveness as a film strength agent was tested on the Timken testing machine using blends of 30 SAE Pennsylvania lubricating oil containing 0.5%, 1.0% and 1.5% of the agent. These blends showed load-carrying capacities respectively of 27,000; 30,800 and 32,000 lbs. per

square inch, while the lubricating oil alone cardissolved in xylol, with sodium, 25% in excess of that theoretically required to remove the chlorine. The reaction was carried out substantially in the manner described in Example 1, but the temperature rose-to 240 to 250 Rafter a portion of the sodium had been added. The final reaction mixture was cooled to room temperature, filtered to remove the sodium chloride, and then washed with water until neutral.

The resulting washed filtrate was dried and then distilled to remove the xylol. Portions of the finished product were blended with 20 SAE Pennsylvania lubricating 011 to make blends containing 0.5%, 1.0% and 1.5%. These blends when tested on the Timken testing machine showed load-carrying capacities of 27,900; 32,000 and 7 29,800 lbs. per square inch; whereas the oil alone had a load-carrying capacity of only 12,380 lbs. per square inch.

Example 3 A mixture oi! di-phosphorus esters containin single and double linkages (CH3CsH4.0) SP=PS(O.CBH4.CH3)

and

(CHa.CcH4.0) 2SPPS (O.CBH4.CH3) 2 After the product was recovered and washed as in'Example 2, portions of it were blended with 20 SAE Pennsylvania lubricating oil to produce blends containing 0.5%, 1.0% and 1.5% of the mixture. These blends showed load-carrying capacities respectively, of 19.350; 25,800; and 24,300, While the Pennsylvania lubricating oil alonehad a load-carrying capacity of only 12,350.

While in the foregoing examples sodium was used to efiect the PP linkage, it is believed that lithium, potassium and finely divided silver, copper and zinc may be employed at least in certain reactions, as is true in the Wurtz-Fittig synthesis. Organic phosphorus chlorides were used in the operations described in the examples primarily for economic reasons, but it is possible to use other organic phosphorus halogen compounds especially the iodides and bromides. While it is believed that the reactions described in connection with the foregoing examples proceed mainly to produce the products indicated, it is possible that minor proportions of other materials are formed, as for example, a compound in which two phosphorus atoms are linked to a third may be produced where mixtures of monoand dichloridesare usedas starting materials.

The examples are given above for the purpose of illustrating the invention, and it is to be understood that R in the general formula may represent an aromatic or aliphatic radical or compound and that either of these may be halogenated or contain other elements such as oxygen or sulfur. Where the ester chloride starting materials contain aliphatic radicals as R the hydrocarbon chain may be straight or branched. Where two (RK) groups are attachced to a single phosphorus one R may be aliphatic and the other aromatic. The (ii-phosphorus esters, in which phosphorus has a valence of 5, may be produced by oxidizing of sulfurizing the di-phosphorus esters in which phosphorus'has a valence of 3. Such compounds of course may be produced, as shown in the examples, by starting with the ester halide in which phosphorus has a valence of 5, as for example (ROhPXCl or (RO)PXC12 where X is oxygen or sulfur directly attached to phosphorus with a double bond.

It is to be understood that while the invention has been described and illustrated in connection with the use .0! the improved compounds as extreme pressure agents in lubricating oils, such compounds are suitable for other purposes as for example in the making. of cutting oils, greases, and for blending with fatty oils, synthetic oils and esters, to produce various types of lubricants. It is to be further understood that the improved compounds may be used directly as lubricants.

Having thus described the invention in its preferred form, what is claimed as new is:

1. An improved mineral oil composition comprising a mineral lubricating oil and a relatively small proportion of a compound having a general formula selected from the. group consisting of (RX) 2P-P(XR):, (RX)P=P(XR),

and (RX) XP=PX(XR), wherein R is an alkyl, an aralkyl or aryl radical and X is an element selected from the group consisting of oxygen and sulfur, said compound having the property of greatly increasing the film strength of the lubricating oil.

2. A composition of matter comprising a mineral oil and a small proportion of a di-phosphorus ester having the general formula wherein R represents a radical selected from the group consisting of alkyl, aryl and aralkyl radicals and X represents an element selected from the group consisting of oxygen and sulfur.

3. A composition of matter comprising a mineral oil and a small proportion of a mixture of organic (ii-phosphorus esters in each of which phosphorus is linked directly to phosphorus.

4. A lubricant comprising an aromatic di-phosphorus ester in which phosphorus is directly linked to phosphorus.

5. A lubricant comprising a cresyl di-phos phorus ester in which phosphorus is directly linked to phosphorus.

6. An improved lubricating oil composition adapted for use at high pressures comprised principally of a mineral lubricating oil and approximately 1% of an organic di-phosphorus ester in which phosphorus is directly linked to phos-' phorus.

7. A composition as defined by claim 6 in which said ester is a cresyl ester.

8. An improved mineral oil composition comprising a relatively large proportion of mineral oil and a relatively small proportion of a Wurtz- Fittig reaction product produced by treating an organic phosphorus halide ester at a temperature V of approximately 200 F. with a Wurtz-Fittig catalyst in proportion suflicient to remove the halide from the ester, said reaction product comprising di-phosphorus esters in which phosphorus is linked directly to phosphorus.

9. A mineral oil composition comprising a relatively large proportion of mineral oil and a relatively small but sufllcient proportion of an extreme pressure agent obtained by reacting an organic phosphorus halide ester at a temperature of approximately 200 F. with a Wurtz-Fittig catalyst in excess of the amount required to remove the halide from the ester, and keeping the reacting constituents at the reaction temperature until substantially all of the halide is removed from the ester.

. ERNEST F. ENGELKE. 

